1. Field Of The Invention:
This invention relates to an apparatus and method which noninvasively detects the existence of cerebral aneurysms in humans and more specifically to an improved system having multiple channels for detecting sound waves created by aneurysms and equipment for analyzing the sound waves.
2. Description Of The Prior Art:
An aneurysm is an abnormal outpouching of the wall of a blood vessel which leaves it vulnerable to enlargement or rupture with severe intracranial hemorrhage. Ruptured aneurysms are a serious clinical problem.
It has been estimated that approximately 28,000 persons suffer a subarachnoid hemorrhage from a ruptured aneurysm annually in North America. The problem is serious because over fifty percent of these patients die and about fifteen percent are severely disabled.
If an aneurysm is detected prior to rupture, it can frequently be treated by the surgical procedure of clip occlusion. This surgery can be performed with a very low rate of complication with an excellent outcome. Once the aneurysm ruptures, however, the clinical condition of the patient deteriorates severely due to the major brain injury which occurs at the time of rupture. Under these conditions, the morbidity and mortality are high in spite of modern advances in treatment.
Up to 60% of individuals who suffer subarachnoid hemorrhage have been reported to exhibit "warning signs" prior to aneurysmal rupture. However, many of the symptoms are nonspecific such as headache, occular pain, and nausea and therefore frequently have been mistaken for a viral illness or for a minor headache. The only way to make a real impact on the outcome of the disease would be to diagnose the problem in individuals exhibiting these vague warning symptoms, or in asymptomatic individuals, by screening populations at risk with noninvasive tests.
There are several known methods for detecting aneurysms before they rupture. One method is angiography. However, this invasive procedure entails expensive hospitalization, trauma and patient risk and therefore is not suited for investigating vague, prodromal symptoms even though those symptoms might precede fatal aneurysm rupture. Thus, a physician faced with possible aneurysm warning signs must judge whether the symptoms warrant the trauma, and expense, of an angiogram.
Ferguson, in J. Neurosurg 36:560-563 (1972), suggested detecting aneurysmal signals by recording sounds from aneurysms exposed at operations using a cardiac phono-catheter which recorded musical sounds from lesions.
Kosugi et al., in Stroke 14 (1) 37-42 (1983), disclosed the use of a "cement wall microphone" (contact accelerometer) in contact with the cranium and the teeth in an attempt to detect aneurysms.
Sekhar and Wasserman, in J. Neurosurg 60:553-559 (1984), disclosed the use of a a Horn-Coupled microphone for non-invasive detection of aneurysms.
Olinger and Wasserman, in Surg. Neurol. 8:298-312 (1977), disclosed the use of air microphone devices for noninvasive detection of aneurysms.
Several United States patents disclose noninvasive aneurysm monitoring techniques. U.S. Pat. No. 4,008,711 discloses a standard electronic low-noise microphone housed in an isolation chamber which detects sound waves from the patient's eyes. These sound waves are converted into an electrical signal which is passed through a final filter to a computer having a Fourier analysis capability. The computer analyzer is disclosed to be a Fourier Analyzer which can output data to a standard CRT or Plotter.
U.S. Pat. No. 4,226,248 discloses a phonocephalographic device having a pair of ear insertable microphones that can detect sounds from the surface and cavities of the head. Amplified signals are processed through a frequency analyzer and can go then to a chart recorder or oscillator.
Despite these known devices, there remains a need for an acoustic aneurysm detector that is designed to more effectively record and analyze the data to aid in the detection of human aneurysms before they rupture.